An ultrasonic transducer, which is used for an ultrasonic diagnostic device, requires fine processing in its manufacturing, and a variety of manufacturing methods are conventionally proposed (for example, Patent Documents 1 and 2).
If an FPC (Flexible Print Circuit) is used as a wiring method for piezoelectric transducers, it is normal to partition the FPC by cutting it with a dicing saw after connecting the FPC to piezoelectric device (for example, Patent Document 1). Patent Document 1 discloses that improvements in stiffness, such as projecting an adhesive on the side of a piezoelectric device, are made to endure a load imposed when the FPC is cut with a dicing saw.
For a body-cavity ultrasonic transducer mounted in an ultrasonic endoscope, etc., its entire size must be reduced to a minimum, and a pain of a patient when an endoscope is inserted must be mitigated. Since the amount of an adhesive for improving stiffness cannot be stipulated with the shape disclosed by Patent Document 1, a size at the time of completion becomes large by an indefinite size, namely, an adhesive.
Especially, if FPC is bent along the side of a backing material, the remaining stress of the stiffness of the FPC becomes higher around piezoelectric elements so that the reliability of wires degrades. Additionally, Patent Document 1 describes that an FPC and piezoelectric transducers are glued. However, if soldering is used, it is difficult to control the amount of solder material. This leads to variations in the load mass of each piezoelectric transducer on vibrations after the FPC is cut down, which exert an influence on the ultrasound characteristic.
As disclosed by Patent Document 2, there is also an example where a conductive adhesive is used as a method other than soldering. According to Patent Document 2, a wiring board is provided on the side of a baching material, and the board and piezoelectric transducers are connected with a conductive adhesive.
However, it is difficult to control the amount of the conductive material to be coated on piezoelectric elements, and besides, the conductive adhesive is coated in an acoustic emission direction (=vibration direction). Therefore, the load mass of each piezoelectric transducer elements increases.    Patent Document 1: Japanese Published Unexamined Patent Application No. H5-3598    Patent Document 2: Japanese Published Examined Patent Application No. S59-20240